Desurfacing apparatus and process



April 1943- I I. P. THOMPSON ETAL 2,317,495

DESURFACING APPARATUS AND PROCESS Filed April 10. 1941 INVENTORS IVAN R THOMPSON EDWARD ME I NCKE BY ATTORNEY Patented Apr. 27, 1943 DESURFACING- APPARATUS AND PROCESS Ivan P. Thompson,

Elizabeth,

and Edward Meincke, Scotch Plains, N. J assignors to The Linde Air Products Company, a corporation of Application April 10, 1941, Serial No. 387,848

Claims.

This invention relates to the art of thermochemically desurfacing metal bodies, such as steel blooms, billets, slabs, etc., especially while such bodies are hot and in transit on conveyor rolls from one rolling mill or other processing apparatus to the next rolling or processing apparatus. Such desurfacing may be performed by nozzles which project gaseous heating and oxidizing streams obliquely against successive portions of the surfaces of the metal bodies to skin, or remove a stratum of metal from, one or more longitudinal surfaces of each metal body during the transit of the latter along the same pass line while supported upon a series of conveyor rolls extending from one stand of rolls to the next.

Ease in starting the desurfacing operation as well as smooth and accurate conveyance of the metal bodies past the desurfacing nozzle or nozzles require that there shall be no wide gap between those rolls of the conveyor table which are nearest to the desurfacing nozzles. Compliance with this requirement, however, shortens the distance between certain desurfacing nozzles and the adjoining conveyor roll or rolls and, as a consequence, hot metal and slag removed from the metal bodies by the desurfacing streams are projected in the direction of treatment and impinge against and become deposited upon the conveyor roll surfaces. 'Such hot metal and slag accumulate on the roll to form one or more collars which encircle and tenaciously adhere to the roll. Such collars interfere with smooth and uniform desurfacing; and, in addition, the adhering molten slag damages the roll surfaces, and the intense heat of the preheat flames as well as the more intense heat of the desurfacing reaction scorches the roll surfaces and increases the tendency of the molten slag to adhere thereto.

Accordingly, the principal object of this invention is to provide an improved procedure and mechanism for thermochemically removing metal from the surfaces of metal bodies such as steel blooms, billets, slabs, etc.

Other objects of the invention are to provide a novel process of and apparatus for progressively maintaining in proper condition and free of ob- Jectionable accumulations, conveyors which are subject to the heat and slag resulting from thermochemical treatment, such as the desurfacing with oxygen of ferrous metal bodies; an improved work conveyor which is simple and economical in its parts, and effective and efficient in operation; and a method of and means for controlling the temperature while cleaning the slag from the conveyor table roll in a thermochemical desurfacing or deseaming machine.

In accordance with the invention there is provided desurfacing apparatus including a desurfacing station provided with desurfacing means for thermochemically treating a ferrous metal body conveyed therethrough. The bodyis moved through the desurfacing station by conveyor means comprising a conveyor roll the surface of which is incidentally subject to an accumulation of slag and molten metal resulting from such thermochemical treatment of the body. Such material is prevented from accumulatingon the surface of the roll by means for conditioning the material for removal from the surface acting in conjunction with means acting on another portion of the roll beyond the region of impingement of the slag for cleaning the so-conditioned material therefrom.

According to the invention, there is also provided a process of progressively maintaining in proper condition, conveyors which are incidentally subject to the heat and'molten material (hereinafter called slag) resulting from thermochemical work treatment, such as desurfacing ferrous metal bodies. Such process preferably comprises applying a slag peeling instrument to the surface of the conveyor, while circulating a cooling medium through the conveyor, and spraying a cooling fluid directly against the slag peeling instrument and the freshly exposed surface area of the conveyor adjacent thereto.

The single figure ofthe drawing is a fragmentary view partly in section and partly in side elevation of apparatus embodying the invention,

Referring to the drawing, there is illustrated, desurfacing apparatus comprising a. conveyor including an upper roll l0 and a lower roll I I adapted to advance a ferrous metal body W through a thermochemical desurfacing station consisting of an upper head l2 and a lower head l3. The heads l2 and I3 are provided with desurfacing nozzles l4 and I5, respectively, for discharging streams of heating and oxidizing gases against the upper and lower surfaces T and B of the body W in the usual mannerto desurface or deseam the latter. The outer surfaces l6 and I1, respectively, of the rolls in and I I, are exposed to the slag resulting from the thermochemical desurfacing of the work surfaces T and B by the desurfacers l2 and I3. Such roll surfaces i6 and [1 are also exposed to the intense heat of preheating flames from the nozzles l4 and I5 during the preheating period and the still more intense heat of the desurfacing reaction, which cause them to become scorched and to permit more readily the adherence of molten slag thereto.

To prevent overheating of the rolls I and II, they are made hollow and a cooling medium, such as water, is circulated through the upper roll ID by a circulating system including an inlet pipe l8 and an outlet pipe l3, and through the lower roll II by a circulating system including an inlet pipe 20 and an outlet pipe 2|. Disposed immediately below the lower roll II is a scraper blade 22 which extends the entire length of the roll II and is slidably fitted into a sleeve 23 secured to a foundation 24. Disposed within the sleeve 23 area series of springs 25 for urging the scraper 22 against the outer surface ll of the roll II. The face 26 of the blade 22 is conformed to the roll surface I1 and has a sharp leading edge 21 for peeling slag therefrom.

Mounted on the foundation 24 by means of a support 28 immediately behind the scraper 22 is a laterally disposed pipe 23 having a series of lineally disposed orifices 33 or directing a spray 3| of cooling fluid, such 'as water, against the outer surface I! of the roll II to form a film on such surface, and against the scraper 22, to cool the latter without chilling the heated body W supported by the roll ll. Maintaining the roll surface I'I cool with the spray 3| is also effective to cause a surface of a molten globule of slag to solidify quickly upon contact with such surface II, which solidification produces rapid contraction, causing such globule to loosen itself and fall free thereof. An arrangement of this character has proven to be very satisfactory since both the roll I l and the blade 22 resist the injurious effects of heat generated during both the preheat and thermochemical reaction periods.

The upper roll it is provided with a slag scraper 32 disposed at the far side thereof in order to facilitate removal of slag peeled therefrom. The scraper 32 is slidably supported by sleeve 33 mounted on foundation 34, and urged into engagement with the roll surface l6 by springs 35; the face 38 of the scraper 32 being conformed to the shape of roll surface l and having a sharp leading edge 31. A support 38 secured to foundation 34 holds a pipe 33 in position parallel to the roll III for directing through orifices 40 a spray ll of cooling fluid, such as water, on the surface areas of the blade 32 and roll surface It forming an included angle between the roll I 0 and blade 32.

In the operation of the illustrated apparatus. either one of the rolls III, II may be omitted entirely along with the corresponding desurfacer l2, l3, in case it is desired to desurface only one surface of the work W. Or, in such case, the omitted roll may be replaced by a conventional mill conveyor roll. However, the illustrated apparatus is particularly useful in case both upper and lower surfaces T and B of the slab or other metal body W are desurfaced simultaneously, and in addition provides pressure means for positively controlling the forward travel of the :body W being desurfaced.

The body W of ferrous metal is advanced in the direction indicated by the arrow from right to left by the rolls I0 and II which are rotated in a clockwise and counter-clockwise direction, respectively, with their outer surfaces l6 and I!- in rolling contact with the top and bottom surfaces T and B, respectively, and the body W. The body W is thus advanced under the desurfacer l2 and above the desurfacer l3, while streams of oxidizing gas surrounded by preheating flames are discharged by the nozzles l4 and I5 against the corresponding top and bottom surfaces T and B of the body W. As the outer surfaces 16 and II of the rolls I 0 and II leave contact with the top and bottom surfaces T and B of the work W. they are exposed to the heat and slag resulting from the thermochemical treatment to which the top and bottom surfaces '1' and B of the body W are subjected by virtue of the operation of thc desurfacers l2 and I3.

The outer roll surfaces I6 and II are progressively maintained in proper condition for successive engagement with the top and bottom surfaces T and B of the body W by the combined temperature controlling and slag cleaning effects of the cooling medium which is continuously circulated through each of the rolls HI and II by the circulating systems including inlet and outlet pipes I 3, l3 and 23, 2|, -respectively; scrapers 22 and 32, respectively, which act to progressively peel slag accumulation from the outer surfaces l6 and I! of the rolls l3 and II as the latter rotate; and sprays 3| and 3|, respectively, of cooling fluid, such as water, which are directed against the roll surfaces l3 and II, respectively, and their scrapers 22 and 32.

By way of example, with the upper roll I! and the upper desurfacer I2 and their associated parts omitted from the apparatus, the driven roll ll may be of the order of 7 inches in diameter and form part of a roll table, with the roll ll placed in front of the nozzles l5 of the lower head l3, as illustrated in the drawing. Such roll ll may be driven through appropriate ratio bevel gears from the countersliafting by which the pinch rolls of the table are driven, so as to have the same peripheral speed as the pinch rolls driving the body B which is desuri'aced.

Actual desurfacing, for example, in accordance with the invention was conducted on bodies W of 1 inch hot rolled SAE 1020 steel, 6 inches wide and 5 feet long, using six Oxweld No. SL-30 nozzles l5 held in nozzle blocks, and arranged for oxygen flow used during the early part of the tests was approximately equal to that recommended for obtaining cuts 1; inch deep; in other words, about 1930 cubic feet per hour. Later cuts were made at the proper oxygen flows to give depths of 3'; inch, and also at higher flows which produced cuts almost 3*, inch deep.

The first cuts were made with the axis of the roll H twenty and one quarter inches in front of the nozzles. This brought the face I] of the roll sixteen and one half inches from the nozzles ll. Under this condition a cut was made using a water spray 3| on the outside ll of the roll II, and water-cooling within it. With this arrangement the roll became very hot after desuri'acing one sample body W, and a continuous ring of slag formed around the roll ll. Although this ring, due to the internal and external cooling, did'not actually adhere, it remained on the roll and would not fall free of its own accord. The roll II was then equipped with a scraper 22 made from a steel angle, which fitted against the roll II with a pressure of about three pounds per inch of length. With the roll in the same position in front of the nozzles as before, and with oxygen flows up to 2500 cubic feet per hour, and resulting desurfacing depths of 0.167 inch, the accumulated slag was removed from the roll in a continuous sheet.

The roll II was then moved so that its center was 15% inches from the nozzles [5, with the roll face 11 /2 inches in front of the nozzles I5.

Again cuts were made at oxygen flows up to 2500 cubic feet per hour corresponding to desurfacing depths of 0.164 inch. As before, the combination of the water spray 3| for wetting the exterior ll of the roll II, the internal watercooling system 20, 2|, and the scraper 22, caused the slag to be removed from the roll I l in a continuous sheet.

A final test resulted in placing the roll center line ten and one quarter inches in front of the nozzles IS, with the face I! six and one-half inches in front of the nozzles I5. Cuts were made at oxygen flows up to 3075 cubic feet per hour resulting in depths of desurfacing cuts up to 0.154 inch. At oxygen flows upto 2500 cubic feet per hour, which was the previous upper limit,

the water spray 3|, internal cooling system 20, 2|, and scraper 22 kept the roll surface I! entirely clean, and caused the slag to be peeled therefrom in a continuous sheet.

In the operation of the apparatus for desurfacing only the bottom surface B of the body W, to remove slag and provide protection for a conveyor table roll, it is desirable to provide internal water cooling, an external water spray, and a scraper blade. Internal cooling of the roll is especially effective in protecting the latter during the starting preheating period. The external spray is especially effective in protecting the scraper from heat and for chilling and conditioning the accumulated slag for removal from the outer surface of the roll. The scraper is especially effective to remove slag from the roll. According to the invention, with a 7 /2 inch diameter roll placed with its center 10% inches in front of six No. SL-SO nozzles, adequate roll maintenance using water and a scraper, can be obtained with oxygen flows up to 2500 cubic feet per hour at a body speed of 50 feet per minute.

A scraper plate pressure of five pounds per inch of roll length is recommended. It is also recommended that, with a roll and nozzles on the underside of the base line, internal water cooling, external water sprays, and a scraper plate, be provided to protect the roll from burning and from slag accumulation; the roll being located so that no part of its outer surface, at a distance of four inches perpendicularly :below the base line, is closer than a length, measured parallel with the base line, of 16% inches in front of the nozzles.

The scraper should be maintained in continuous contact with the roll, and never leave it during the desurfacing operation. Therefore, while the scraper preferably is held against the roll by springs, any other suitable device, such as counterweights, screws, etc., may be used for accomplishing such desired result. Also, in some cases it may be necessary to use a greater force than that recommended above to maintain contact between the scraper and a roll having a rough surface, for example. If any slag gets between the scraper and the roll, the scraper is moved from contact with the roll surface and a slag ring forms on the roll. It is, therefore, quite important that the mechanism for holding the scraper in contact with the roll be positive enough at all times to prevent slag from getting between the scraper and the roll.

While the description of the apparatus shown in the drawing refers particularly to desurfacing operations on the upper or lower or upper and lower surfaces of a ferrous metal member, it is to be understood that such description is by way of example and is not intended to exclude from the scope of the invention, edge desurfacing or where rolls are mounted vertically and also require substantially the same treatment as upper or lower rolls.

What is claimed is:

1. Desurfacing apparatus including a desurfacing station provided with desurfacing means for thermochemically treating a ferrous metal body conveyed therethrough, conveyor means for moving said body through said desurfacing station, said conveyor means comprising a conveyor roll the surface of which is incidentally subject to an accumulation of slag resulting from such thermochemical treatment of said body, means for preventing said slag from accumulating on the surface-of said roll, comprising means for conditioning said slag for removal from said surface, and means for removing the so-conditioned slag from said surface.

2. Desurfacingapparatus including a desurfacing station provided with desurfacing means for .thermochemically treating a ferrous metal body conveyed therethrough, conveyor means for moving said body through said desurfacing station, said conveyor means comprising a conveyor roll the surface of which is incidentally subject to an accumulation of slag resulting from such thermochemical treatment of said body, means for preventing said slag from accumulating on the surface of said roll, comprising means for progressively conditioning said slag for peeling from said surface, and means for progressively peeling the-so-conditioned slag from said surface.

3. Thermochemical apparatus including a thermochemical station provided with means for thermochemically treating a ferrous metal body conveyed therethrough, conveyor meansf or moving said body through said thermochemical station, said conveyor means comprising a conveyor roll the surface of which is incidentally subject to an accumulation of slag resulting from such thermochemical treatment of said body, means for preventing said slag from accumulatingon the surface of said roll, comprising means for chilling said roll to condition said slag for removal from said surface, and means for scraping the so-conditioned slag from said surface.

4. Apparatus comprising the combination with a hollow roll and a device for thermochemlcally acting on a metal body so as to produce a slag, said device being positioned with respect to said roll so that at least a portion of such slag impinges on said roll, of a slag scraper blade mounted for cooperation with said roll surface to clean slag therefrom as the rollrotates, means adapted to urge said blade into operative relation with said roll surface, means for spraying a cooling fluid, such as water, against said roll surface so that said cooling fluid also cools said blade, and means for circulating a cooling medium, such as water, through said hollow roll.

conveyor rolls, of means for progressively maintaining the outer work engaging surfaces of said conveyor rolls in proper cond'tion, comprising a scraper engaging each roll surface beyond the region of impingement of such slag thereon for progressively peeling slag therefrom, means for continuously circulating a cooling medium, such as water, through said conveyor rolls, and means for continuously spraying a cooling fluid, such as water, against the outer surface of each conveyor roll to the rear of said scraper.

6. Process of progressively maintaining in proper condition a conveyor which is incidentally subject to the heat and slag resulting from thermochemical work treatment, such as desurfacing ferrous metal bodies, which comprises applying a slag peeling instrument to the surface of the conveyor, circulating a cooling medium through said conveyor, and spraying a cooling fluid directly against said slag peeling instrument and the freshly exposed surface area of said conveyor adjacent thereto.

7. Process of progressively maintaining in propercondition a mill conveyor roll which is incidentally subject to the heat and slag resulting from thermochemical work treatment, such as desurfacing ferrous metal bodies, which comprises peeling slag from the conveyor roll as it accumulates thereon, and spraying a cooling fluid, such as water, against that surface area of said roll from which the slag has been most recently peeled.

8. Process of progressively maintaining in proper condition a mill conveyor roll which is incidentally subject to the heat and slag resulting from thermochemical work treatment, such as desurfacing ferrous metal bodies, which comprises peeling slag from the conveyor roll as it accumulates thereon, circulating a cooling medium, such as water, through said roll, and spraying a cooling fluid, such as water, against that surface area of said roll from which the slag has been most recently peeled.

9. Process of progressively maintaining in proper condition a mill conveyor roll which is incidentally subject to the heat and slag resulting from thermochemical work treatment such as desurfacing ferrous metal bodies, which comprises applying a scraper to the surface of the conveyor roll to peel slag therefrom, circulating a cooling medium, such as water, through said roll, and spraying a cooling fluid, such as water, against said scraper and said roll in the included angle formed between said scraper and that surface area of said roll from which the slag has been peeled.

10. Process of progressively maintaining in 6 proper condition a roll which is incidentally subject to the impingement thereon of heat and molten slag containing metal resulting from thermochemical work treatment, such as desurfacing ferrous metal bodies, which comprises ro- 10 tating said roll, applying a cooling medium to form a film on the surface of said roll prior to such impingement, and then peeling the adherent chilled slag containing molten metal from the surface of said roll.

11. Process according to claim 10, which includes spraying a cooling fluid against said conveyor roll after the slag containing metal has been peeled from said roll.

12. Thermochemical apparatus according to claim 3 wherein said means for chilling said r011 comprises means for continuously spraying a cooling fluid against said scraping means and said surface of said roll.

13. Thermochemical apparatus including a thermochemical station provided with mean for thermochemically treating a ferrous metal body conveyed therethrough, conveyor means for moving said body through said thermochemical station, said conveyor means comprising a conveyor roll so positioned with respect to said means for thermochemically treating such body that the surface of said roll is subject to an accumulation of slag resulting from such thermochemical treatment of said body, and means for scrapin the slag from said conveyor roll.

14. Apparatus including a device for progressively thermochemlcally treating a surface of a metal body, such treatment producing a molten slag a substantial portion of which is projected 40 in the direction of treatment, and means for intercepting such projected slag comprising a rdtatable roll arranged in a position with respect to said device to receive such projected slag on a portion of its surface, and means acting on another portion of said roll beyond the region of impingement of said slag for removing portions of slag accumulated thereon as said roll rotates.

15. Apparatus according to claim 14 including means for directing a cooling fluid against 5 at least a portion of the slag collecting surface of said roll.

. IVAN P. THOMPSON.

EDWARD MEINCKE. 

